1. Field of the Invention
The present invention relates to toothbrushes body preform molding device and toothbrush body preform to be provided with buffer cap on the backs of their bristle implanting heads.
2. Description of the Prior Art
As well known to those skilled in the art, a typical toothbrush is manufactured by implanting a plurality of bristle bases into the stick-shape or hexahedral hard head of the toothbrush body preform. In the typical toothbrush, the hard bristle base implanting head as well as the handle may scratch the periodontal tissue surface and the oral cavity when brushing the tooth. In this regard, the above hard toothbrush may have a bad effect on the oral hygiene.
In an effort to overcome the above problem, Japanese Utility Model Laid-open Publication No. Heisei. 4-6926 discloses a toothbrush having a relatively thicker soft member mounted on the brush head surface. When implanting the bristles in the above toothbrush, the bristle bases are implanted in the soft member. This toothbrush, while providing somewhat elasticity for the bristle base implanting portion of the brush head, nevertheless has a problem that it can not achieve the desired elasticity of the toothbrush body. In this regard, this toothbrush still may scratch the periodontal tissue surface and the oral cavity and exert a bad influence upon the oral hygiene.
Japanese Utility Model Laid-open Publication No. Sho. 57-148332 discloses a toothbrush having a cushion rubber covering the bristle base implanting portion of the brush head. However, the above application represents neither the mounting strength of the cushion rubber nor the method of how to mount the cushion rubber on the toothbrush head. In this regard, the above toothbrush may not be practically used. Otherwise stated, the toothbrush having the cushion rubber about its head may exert a bad influence upon the oral hygiene and achieve no desired endurance of the cushion rubber.
Germany Patent No. DE 3628722 discloses a toothbrush having a handle with a head, made of plastics by injection molding, with a rigid setting for the material. In this toothbrush, both the narrow sides and the top of brush head are coated by an elastomer or a plastomer with a softer setting. The troble of the Germany patent does not disclose how to rigidly fix the coating material to the brush head through a conventional injection molding. Considering that the elastic material like rubber and the hard head material are quite different from each other in their melting points, their bonding forces and their percentages of contraction sticking two different material enough to use in sanitary objects in mass production never has been developed.